I could watch Riz Ahmed in almost anything, but there are limits, tested here by this deeply mediocre British mystery thriller. Adapted by Patrick Neate from his 2005 novel, City of Tiny Lights is helmed by Pete Travis, who in 2012 nearly rescued Judge Dredd from comic book movie hell. But while Travis transposes some of Dredd’s style, he cannot bring its boldness, humour or efficiency.

Ahmed plays Tommy Akhtar, a “snoop” who is so underground that even his job description is unclear. Basically, he’s a private detective. One day he’s visited by a working woman named Melody (Cush Jumbo). Her flatmate is missing. Tommy investigates and finds the body of a Pakistani businessman. It’s a discovery that will bring him into close contact with two blasts from his past: old flame Shelley (Billie Piper), and smarmy friend “Lovely” (James Floyd).

A series of flashbacks (complete with dodgy house music from 1997) reveals what happened between the three teenage friends – and the fate of a fourth, the father of Shelley’s child. Movies adopting parallel storylines are only as strong as their weakest thread, and I’ll say upfront that the flashbacks are dull and consistently knock the wind out of the present-day sections.

Tommy’s investigation leads to him being sandwiched between an Islamic Youth organisation and some sinister US feds. There’s little depth or plausibility to the depiction of either institution, although at least the Islamic Youth part makes an effort to highlight the notion that terrorism can arise not purely from powerful ideological rhetoric, but from laudable community concerns.

Needless to say, Tommy is going to get “in too deep” and be haunted by the ghosts of his past. It’s all pretty grim and intense, although we do get some light relief from the peerless Roshan Seth as Tommy’s father, Farzad. An ex-serviceman with charisma to spare but no one with whom to share it, Farzad is the most rounded character by far, and the most movingly portrayed.

Actually, all the main performances are pretty good. Ignoring that Ahmed looks distinctly gym-fit for a functioning alcoholic and chain-smoker, he brings an inward intensity to the role of a man whose worst memories are returning to him. Piper is more extrovert in her portrayal; she gives good grief, even if her character is somewhat one-note.

No, the problems are stylistic, structural and semantic. In terms of style, City of Tiny Lights comes off like a lame imitation of Michael Mann in Collateral mode, all intimate close-ups and midnight moodiness. But there’s no dramatic heft behind the cinematic posturing; no convincing characterisation or surprising storytelling to keep a firm grip on our attention. And the editing is a disastrous mix of messy action and needless post-prod frame-stuttering effects.

The script fares little better. Aside from superfluous bookend narrations from Ahmed, there’s some excruciating wannabe hard-boiled dialogue. “I wouldn’t have you down as the sensitive type,” someone says. Tommy replies, “Only when I shave.” It’s the kind of nonsensical response which we could forgive if the setting were 1930s Chicago and not 2010s London.

(That’s another thing: the conspicuous lack of mobile phone use by the characters. It’s relevant as many of the dramatically last-second, face-to-face encounters could be eliminated if the characters stopped acting like it was… well, 1997.)

The clockwork innards of the screenplay are always visible. Certain characters are clearly dodgy from the start, but super-sleuth Tommy is blind to it. Others conceal information for no better reason than serving the narrative ebb and flow. And eyebrow-curling incidents abound. At one point Shelley’s early-teenage daughter suddenly visits Tommy at his office in the middle of the night to ask him about her father. Once we’ve been fed a little more of the boring backstory, she scuttles away again, as if conscious of spoiling too much of the parallel plotline.

It’s disappointing because the elements are here for an entertaining and atmospheric neo-noir. This is an original setting in which to play with some classical genre traits, and it has in its grasp an engaging leading ensemble. But on the other side of the camera, too few involved seem to have got the memo: it looks and sounds cheap in almost every aspect. An opportunity wildly missed.